/**
 * @Auther: ayo
 * @Date: 2018/8/22 12:39
 * @Description: // TODO
 */
import { Injectable } from '@angular/core';

@Injectable()
export class Base64Util {

    // private property
    _keyStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

    constructor() {
    }

    // public method for encoding
    encode(input) {
        let output = '';
        let chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        let i = 0;
        input = this._utf8_encode(input);
        while (i < input.length) {
            chr1 = input.charCodeAt(i++);
            chr2 = input.charCodeAt(i++);
            chr3 = input.charCodeAt(i++);
            enc1 = chr1 >> 2;
            enc2 = (
                       (
                           chr1 & 3) << 4) | (
                       chr2 >> 4);
            enc3 = (
                       (
                           chr2 & 15) << 2) | (
                       chr3 >> 6);
            enc4 = chr3 & 63;
            if (isNaN(chr2)) {
                enc3 = enc4 = 64;
            } else if (isNaN(chr3)) {
                enc4 = 64;
            }
            output = output + this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) + this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);
        }
        return output;
    };

    // public method for decoding
    decode(input) {
        let output = '';
        let chr1, chr2, chr3;
        let enc1, enc2, enc3, enc4;
        let i = 0;
        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, '');
        while (i < input.length) {
            enc1 = this._keyStr.indexOf(input.charAt(i++));
            enc2 = this._keyStr.indexOf(input.charAt(i++));
            enc3 = this._keyStr.indexOf(input.charAt(i++));
            enc4 = this._keyStr.indexOf(input.charAt(i++));
            chr1 = (
                       enc1 << 2) | (
                       enc2 >> 4);
            chr2 = (
                       (
                           enc2 & 15) << 4) | (
                       enc3 >> 2);
            chr3 = (
                       (
                           enc3 & 3) << 6) | enc4;
            output = output + String.fromCharCode(chr1);
            if (enc3 !== 64) {
                output = output + String.fromCharCode(chr2);
            }
            if (enc4 !== 64) {
                output = output + String.fromCharCode(chr3);
            }
        }
        output = this._utf8_decode(output);
        return output;
    };

    // private method for UTF-8 encoding
    private _utf8_encode(string) {
        string = string.replace(/\r\n/g, '\n');
        let utfText = '';
        for (let n = 0; n < string.length; n++) {
            const c = string.charCodeAt(n);
            if (c < 128) {
                utfText += String.fromCharCode(c);
            } else if ((
                           c > 127) && (
                           c < 2048)) {
                utfText += String.fromCharCode((
                                                   c >> 6) | 192);
                utfText += String.fromCharCode((
                                                   c & 63) | 128);
            } else {
                utfText += String.fromCharCode((
                                                   c >> 12) | 224);
                utfText += String.fromCharCode((
                                                   (
                                                       c >> 6) & 63) | 128);
                utfText += String.fromCharCode((
                                                   c & 63) | 128);
            }
        }
        return utfText;
    };

    // private method for UTF-8 decoding
    private _utf8_decode(utfText) {
        let string = '';
        let i = 0;
        let c, c1, c2 = 0;
        while (i < utfText.length) {
            c = utfText.charCodeAt(i);
            if (c < 128) {
                string += String.fromCharCode(c);
                i++;
            } else if ((
                           c > 191) && (
                           c < 224)) {
                c1 = utfText.charCodeAt(i + 1);
                string += String.fromCharCode((
                                                  (
                                                      c & 31) << 6) | (
                                                  c1 & 63));
                i += 2;
            } else {
                c1 = utfText.charCodeAt(i + 1);
                c2 = utfText.charCodeAt(i + 2);
                string += String.fromCharCode((
                                                  (
                                                      c & 15) << 12) | (
                                                  (
                                                      c1 & 63) << 6) | (
                                                  c2 & 63));
                i += 3;
            }
        }
        return string;
    }
}
